Method of constructing asphalt macadam surface courses



June 27, 1933.

L. R. MAsoN ET AL METHOD OF CONSTRUCTING ASPHALT MACADAM SURFACE COURSES Filed May 31, 1930 INVENTOR MHQO/DZMQSQ? W L. W ATTORNEY Patented June 27, 1933 UNITED STATES PATENT OFFICE LANDON R. MASON, OF LOS ANGELES, AND FRED E. GRIFFITH, OF LONG BEACH, CALI- FORNIA, ASSIGNORS, BY MESNE ASSIGNMENTS, TO WILLIAM. C. MCDUFFIE, BE- CEIVER FOR RICHFIELD OIL COMPANY OF CALIFORNIA, A CORPORATION OF DELA- WARE METHOD OF CONSTBUOTING ASPHALT EAOADAM SURFACE COURSE Application filed Kay 31,

as completely as possible without the use ofexcess amounts, in order that no surplus asphalt will rise to the surface of'the pavement.

becomes soft and to shift or become wavy.

Also a surfaced course which has been constructed and subjected to traflic conditions to adsorb the excess asphalt.

in hot weather may bleed and become sticky due to excess amounts of low melting point asphalt having been used in the construction, thereby requiring a re-application of fine aggregate such as sand or stone dust It is well known in the art of constructing surface courses such as streets or road-ways that these difliculties may be overcome by employing what is known as asphaltic concrete which is a mixture of stone aggregate containing the required amount of a high melting point asphalt, just sufficient to completely coat the stones of the aggregate without using excess amounts. Asphaltic concrete is made by mixing asphalt with coarse and fine stone aggregate ina mixing device at an elevated temperature suflicient to expel all water from the stone aggregate and maintain the asphalt in a fluid condition, after which the asphaltic concrete or surface 1930. Serial No. 458,894.

course mixture in a heated condition is transported and spread upon the prepared dry surface or road-way to be paved and then immediately, while hot, compacted by heavy rollers. Therefore the cost for surfacing road-ways or other courses with asphaltic concrete is much greater than with asphalt macadam pavement.

Now we have discovered an improvement in surfacing courses by means of which a road-way, street, or other course, may be constructed by the asphalt macadam surfacing method, in which a pavement superior in tensile strength as compared to the asphalt macadam pavement can be constructed and one which is approximately equal in durability to asphalt concrete surfaced courses at a cost which is approximately not greater than the cost of constructing the well-known asphalt macadam pavement.

' Our improvement-consists in the use of an asphalt containing finely divided diatomaceous earth,-which after mixing will remain suspended in hot melted asphalt and may be spread by means of spray nozzles or other mechanical pressure Spreaders upona prepared surface of compacted stone aggregate, the diatomaceous earth being in quantities suflicient to raise the melting oint of the asphaltto such a degree that the ment will not bleed or become soft or sticky and will not shift or buckle in hot weather. We have determined that the quantit bf diatomaceous earth which has been pu verized to such a degree that the diatom shells are substantially separated from each other, ranges from approximately 2 per cent by weight to as high as 15 per cent by weight or higher, the percentage employed depending upon the penetration of the asphalt employed and the degree of penetration and tensile strength required to prevent the asphalt mixture from'becoming soft or sticky in hot weather and from cracking in cold weather.

ed pave- The penetration of the asphalt or road oil employed may range from approximately 7.5 mm. to 25.0 mm. (New York Testing 500 degrees F. is introduced into an insulated mixer of any well-known type. Preferably a mechanical mixer is employed such as a mixer with revolving paddles or one which employs a circulating agitation through a pump, or, the diatomaceous earth may be mixed with the melted asphalt at the aforestated temperatures in a tank wagon spreader by a circulating agitation. The diatomaceous earth is preferably heated to a temperature above the boiling point of water to expel free water, and below the temperature of the heated fluid asphalt. Preferably, a temperature of approximately 250 to 300 degrees F. is employed, although it is to be understood that the diatomaceous earth may be added to the hot asphalt without being heated. The object of heating the diatomaceous earth before addition to the heated asphalt is mainly to prevent loss of heat of the mixture.

' We are aware that it is well-known in the art to mix diatomaceous earth with the heated fluid asphalt and then mix the same with heated stone aggregate to produce asphaltic struct improved asphalt macadam surface courses by spraying hot melted asphalt containing diatomaceous earth through a pressure distributor upon compacted stone aggregates in quantities sufficient to cement the layers of stone to produce a pavement which will not become soft or sticky in hot weather, or crack in cold weather.

Another object of the invention is to construct a durable asphalt macadam pavement of increased tensile strength and flexibility at a minimum cost.

A preferred example of the application of our invention will now be given as carried out in the paving of a road-way, reference bein made to the accompanying drawing in w ich:

Figure 1 represents the first stage in the making of the pavement.

Figure 2 shows a second stage with" the intermediate size stone aggregate after rolling and compactingand igure 3 the finished roadway with fine stone aggregate compacted and cemented into the voids of the intermediate stone aggregate.

a shows a graded roadway with coarse stone aggregate 5 compacted and cemented in place by the asphalt diatomaceous earth mixture 6. These are arranged as shown in Figure 1 and after rolling, the stone aggregate 7 is applied and compacted and in the last stage, illustrated in Figure 3, the aggregate 8 is added and compacted and cemented into the voids of the intermediate stones 7.

The road-way is first graded to the desired level, compacted by rolling and cleaned of all loose and foreign material. Clean coarse aggregate 5 is then spread upon the base 4 in a uniform loose layer of correct thickness and rolled with a power driven roller until compacted to a uniform surface. Upon the rolled, dry, coarse aggregate surface, hot asphalt at a temperature ranging from approximately 300 to 500 degrees F. containing approximately 10 per cent by weight of suspended pulverized diatomaceous earth, designated as 6 is uniformly applied by means of spray nozzles or other mechanical pressure distributors at the rate of approximately 1 to 3 gallons of the asphalt mixture per square yard. llf the distributor is provided with heating means the asphalt containing the diatomaceous earth is circulated and agitated throughout the entire heating bution of the intermediate aggregate, the

road surface is again rolled until the intermediate stone aggregate is completely embedded into the coarse aggregate and asphalt-diatomaceous earth mixture 6 to such a degree that there will be substantially no voids in the road surface and the surface is hard, smooth and shows no movement under the roller. N

After the intermediate aggregate has been rolled the pavement is swept clean and treated with a second application of asphalt contaming approximately 10 per cent by weight of diatomaceous earth at a temperature of approximately 300 to 500 degrees F., being substantially the same as employed in the first treatment, although higher or lower percentages of diatomaceous earth: may be used, depending upon the grade of asphalt employed and the thickness of the seal or top coat specified. The quantityof hot asphaltdiatomaceous earth mixture may range from A to 1 gallon or more per square yard for the seal coat. I

After this second application of hot asphalt containing diatomaceous earth, and preferably while still warm, fine dry stone aggregate or sand, fine dry stone aggregate or sand containing diatomaceous earth, or

\ on the road surface, after which the road surface may be again rolled after a period ranging from 5 to 10 days, thereby completing the construction of the pavement.

While the process herein described is well I adapted for carrying out the objects of this invention, various modifications and-changes may be made without departing from the spirit of the invention, and the invention includes all such changes and modifications as come within the scope of the appended claims.

What we claim is:

1. A method of constructing asphalt macadam surface courses, comprising, spreadlng and compacting by rolling a layer of coarse stone aggregate on a course, spraying the compacted layer of coarse stone aggregate with hotliquid asphalt containing pulverized diatomaceous earth and cementing the compacted layer of coarse stone aggregate in place,,then spreading a layer of intermediate size stone aggregate over the cemented layer of coarse stone aggregate, and compacting by rolling the layer of intermediate size stone aggregate until the intermediate size stone aggregate is embedded and cemented into the voids of the coarse stone aggre to, spraying 'the surface of the compacte cemented layers of stone aggregates with hot liquid asphalt containing diatomaceous earth, then spreading a layer of stone aggregate and diatomaceous earth over the surface of the sprayed cemented layers of stone aggregates, and bonding by rolling the layer of stone aggregate and diatomaceous earth to the surface of the cemented layers of stone aggregates on the course.

2. A method of constructing asphalt mac- & adam surface courses, comprising, spreading and compacting by rolling a layer of coarse stone aggregate on a course, spraying the compacted layer of coarse stone aggregate with hot liquid asphalt containing pulverized diatomaceousearth and rcementing the compacted layer of coarse stone aggregate in place, then spreading a layer of intermediate size stone aggregate over the cemented layer of coarse stone aggregate, and compacting by rolling the layer of intermediate size stone aggregate until the intermediate size stone aggregate is embedded and cemented into the voids of the coarse stone aggregate,

spraying the surface of the compacted cemented layers of stone aggregates with hot liquid asphalt containing diatomaceous earth, then spreading a layer of diatomaceous earth over the surface of the sprayed cep mented layers of stone aggregates, and'bonding by rolling the layer of diatomaceous earth to the surface of the cemented layers of stone aggregates on the course.

3. A method of constructing asphalt mac- I adam surface courses, comprising, spreading and compacting by rolling a layer of coarse stone aggregate on a course, spraying the compacted layer of coarse stone aggregate with hot liquid asphalt containing pulverized diatomaceous earth and cementing the compacted layer of coarse stone aggregate in place, then spreading a layer of intermediate size stone aggregate over the cemented layer of coarse stone aggregate, and compacting by rolling the layer of intermediate size stone aggregate until the intermediatesize stone aggregate is embedded and cemented into the yoids of the coarse stone aggregate, spray- .mg the surface of the compacted. cemented layers of stone aggregates with hot liquid asphalt containing diatomaceous earth, then spreading a layer of fine stone aggregate over the surface of the sprayed cemented layers of stone aggre ates, and bonding by rolling the layer of ne stone aggregate to the sug' 'face of the cemented layers of stone aggregates on the course.

4. A' Inethod of constructing asphalt macadam surface courses, comprising, spreading and compacting. by rolling a layer of coarse stone ,-aggregate on a course, spraying the compacted layer of coarse stone aggregate with hot liquid asphalt containing approxi- I mately ten percent by weight pulverized diatomaceous earth, and cementing the compacted layer of coarse stone aggregate in place, then spreading a layer of intermediate size stone aggregate over the cemented layer of coarse stone aggregate, and compacting by rolling the layer of intermediate size stone aggregate until the intermediate size stone aggregate is embedded and cemented into spraying the surface of the compacted oemented layers of stone aggregates with hot liquid asphalt containing approximately ten percent by weight diatomaceous earth, then spreading a layer of stone aggregate and lliltOlllflCQOllS earth over the surface of the sprayed ceme'nted layers of stone aggregates, and bonding by rolling the layer of stone aggregate and diatomaceous earth to the surface of the cemented layers of stone aggregates on the course.

5. A method of constructing asphalt macadam courses. comprising spreading and compacting by rolling a layer of coarse stone aggregate on a course. spraying the compacted coarse stone aggregate with hot liquid asphaltcontaining diatom shells filled with the asphalt, in quantities sufiicient to coat.

and cement the compacted coarse stone aggregate 111 place, spreading a layer of intermediate size stone aggregate over the cemented layer of coarse stone aggregate and rolling the layer of intermediate size stone aggregate until the intermediate size stone aggregate is embedded and cemented into the voids of the coarse stone aggregate, spraying the surface of the cemented layers of aggregates with hot asphalt containing diatom shells filled with the asphalt, then spreading fine stone aggregate containing diatomaceous earth over the sprayed surface, and rolling the layer of fine stone aggregate containing diatomaceous earth until compacted, cemented and bonded to the surface of the cemented coarser stone aggregates.

In testimony whereof we afix our signatures.

LANDON R. MASON. FRED E. GRIFFITH. 

